Chicago weather: Heat, humidity build as severe storm threat grows

CHICAGO - Heavy overnight rains, especially in the city and south — and in particular in parts of northwest Indiana — are moving away early this morning.

While additional showers and isolated thunderstorms can’t be ruled out, even some morning drizzle, the vast majority of the day will simply be very warm and very humid with highs in the mid 80s.

Tonight presents an opportunity for a stronger thunderstorm, especially after midnight. Not all computer models are showing this, however, so this remains a low-probability event, but one that we will need to monitor just in case. For me, the greatest chances of strong severe thunderstorms will occur late Wednesday night and Thursday afternoon.

What's next:

Wednesday will likely be the hottest day of the year so far when high temperatures should crack the 90° mark for the first time. There will be enough humidity to produce heat indexes close to 100°. Most of the day will simply be partly sunny and breezy. Late at night is when a cluster of thunderstorms is likely to plow through the area and there is a risk of damaging wind gusts with that system.

Thursday will have partly sunny skies and perhaps a residual early morning shower. But the main show arrives in the afternoon when a line of intense thunderstorms will barrel through our area. There is a risk of severe weather during this period with all hazards in play. Once those storms move out of the area Thursday night, it should be quiet and not as warm moving forward for at least a day and a half.

Friday looks mostly sunny and pleasant with highs in the low 80s.

Over the weekend, the majority of the time will be rain-free and pleasant with highs both days in the mid to upper 70s. There’s a chance of showers and thunderstorms arriving Saturday night and continuing into early Sunday.